A Comparison of Usage and Outcomes Between Nurse Practitioner and Resident-Staffed Medical ICUs.

OBJECTIVE: To compare usage patterns and outcomes of a nurse practitioner-staffed medical ICU and a resident-staffed physician medical ICU. DESIGN: Retrospective chart review of 1,157 medical ICU admissions from March 2012 to February 2013. SETTING: Large urban academic university hospital. SUBJECTS: One thousand one hundred fifty-seven consecutive medical ICU admissions including 221 nurse practitioner-staffed medical ICU admissions (19.1%) and 936 resident-staffed medical ICU admissions (80.9%). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Data obtained included age, gender, race, medical ICU admitting diagnosis, location at time of ICU transfer, code status at ICU admission, and severity of illness using both Acute Physiology and Chronic Health Evaluation II scores and a model for relative expected mortality. Primary outcomes compared included ICU mortality, in-hospital mortality, medical ICU length of stay, and post-ICU discharge hospital length of stay. Patients admitted to the nurse practitioner-staffed medical ICU were older (63 ± 16.5 vs 59.2 ± 16.9 yr for resident-staffed medical ICU; p = 0.019), more likely to be transferred from an inpatient unit (52.0% vs 40.0% for the resident-staffed medical ICU; p = 0.002), and had a higher severity of illness by relative expected mortality (21.3 % vs 17.2 % for the resident-staffed medical ICU; p = 0.001). There were no differences among primary outcomes except for medical ICU length of stay (nurse practitioner-resident-staffed 7.9 ± 7.5 d vs resident-staffed medical ICU 5.6 ± 6.5 d; p = 0.0001). Post-hospital discharge to nonhome location was also significantly higher in the nurse practitioner-ICU (31.7% in nurse practitioner-staffed medical ICU vs 23.9% in resident-staffed medical ICU; p = 0.24). CONCLUSIONS: We found no difference in mortality between an nurse practitioner-staffed medical ICU and a resident-staffed physician medical ICU. Our study adds further evidence that advanced practice providers can render safe and effective ICU care.

Sarcoidosis activates diverse transcriptional programs in bronchoalveolar lavage cells.

BACKGROUND: Sarcoidosis is a multisystem immuno-inflammatory disorder of unknown etiology that most commonly involves the lungs. We hypothesized that an unbiased approach to identify pathways activated in bronchoalveolar lavage (BAL) cells can shed light on the pathogenesis of this complex disease. METHODS: We recruited 15 patients with various stages of sarcoidosis and 12 healthy controls. All subjects underwent bronchoscopy with lavage. For each subject, total RNA was extracted from BAL cells and hybridized to an Affymetrix U133A microarray. Rigorous statistical methods were applied to identify differential gene expression between subjects with sarcoidosis vs. CONTROLS: To better elucidate pathways differentially activated between these groups, we integrated network and gene set enrichment analyses of BAL cell transcriptional profiles. RESULTS: Sarcoidosis patients were either non-smokers or former smokers, all had lung involvement and only two were on systemic prednisone. Healthy controls were all non-smokers. Comparison of BAL cell gene expression between sarcoidosis and healthy subjects revealed over 1500 differentially expressed genes. Several previously described immune mediators, such as interferon gamma, were upregulated in the sarcoidosis subjects. Using an integrative computational approach we constructed a modular network of over 80 gene sets that were highly enriched in patients with sarcoidosis. Many of these pathways mapped to inflammatory and immune-related processes including adaptive immunity, T-cell signaling, graft vs. host disease, interleukin 12, 23 and 17 signaling. Additionally, we uncovered a close association between the proteasome machinery and adaptive immunity, highlighting a potentially important and targetable relationship in the pathobiology of sarcoidosis. CONCLUSIONS: BAL cells in sarcoidosis are characterized by enrichment of distinct transcriptional programs involved in immunity and proteasomal processes. Our findings add to the growing evidence implicating alveolar resident immune effector cells in the pathogenesis of sarcoidosis and identify specific pathways whose activation may modulate disease progression.

Lung cancer screening beyond low-dose computed tomography: the role of novel biomarkers.

Lung cancer is the most common and lethal malignancy in the world. The landmark National lung screening trial (NLST) showed a 20% relative reduction in mortality in high-risk individuals with screening low-dose computed tomography. However, the poor specificity and low prevalence of lung cancer in the NLST provide major limitations to its widespread use. Furthermore, a lung nodule on CT scan requires a nuanced and individualized approach towards management. In this regard, advances in high through-put technology (molecular diagnostics, multi-gene chips, proteomics, and bronchoscopic techniques) have led to discovery of lung cancer biomarkers that have shown potential to complement the current screening standards. Early detection of lung cancer can be achieved by analysis of biomarkers from tissue samples within the respiratory tract such as sputum, saliva, nasal/bronchial airway epithelial cells and exhaled breath condensate or through peripheral biofluids such as blood, serum and urine. Autofluorescence bronchoscopy has been employed in research setting to identify pre-invasive lesions not identified on CT scan. Although these modalities are not yet commercially available in clinic setting, they will be available in the near future and clinicians who care for patients with lung cancer should be aware. In this review, we present up-to-date state of biomarker development, discuss their clinical relevance and predict their future role in lung cancer management.

Readmissions after hospital discharge with acute exacerbation of COPD: are we missing something?

Acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is an important part of the disease's morbidity, mortality, and progression, and is associated with increasing utilization of health care resources. The concept of integrated care based on a chronic care model is relatively new to chronic obstructive pulmonary disease, but has proved successful in improving clinical outcomes and probably in decreasing health care utilization in other chronic conditions. A comprehensive approach is needed to target a change in behavioral patterns in patients, increase physician's awareness and adherence to evidence-based recommendations, and address system related issues. This article discusses the evidence for various facets of nonpharmacological management of AECOPD and proposes a model of care that might be the missing link for reducing hospital readmissions for AECOPD. This model may decrease the morbidity, slow disease progression, and curb the increasing health care resource utilization without compromising patient care.

Carbon nanotube-induced pulmonary granulomatous disease: Twist1 and alveolar macrophage M1 activation.

Sarcoidosis, a chronic granulomatous disease of unknown cause, has been linked to several environmental risk factors, among which are some that may favor carbon nanotube formation. Using gene array data, we initially observed that bronchoalveolar lavage (BAL) cells from sarcoidosis patients displayed elevated mRNA of the transcription factor, Twist1, among many M1-associated genes compared to healthy controls. Based on this observation we hypothesized that Twist1 mRNA and protein expression might become elevated in alveolar macrophages from animals bearing granulomas induced by carbon nanotube instillation. To address this hypothesis, wild-type and macrophage-specific peroxisome proliferator-activated receptor gamma (PPARγ) knock out mice were given oropharyngeal instillation of multiwall carbon nanotubes (MWCNT). BAL cells obtained 60 days later exhibited significantly elevated Twist1 mRNA expression in granuloma-bearing wild-type or PPARγ knock out alveolar macrophages compared to sham controls. Overall, Twist1 expression levels in PPARγ knock out mice were higher than those of wild-type. Concurrently, BAL cells obtained from sarcoidosis patients and healthy controls validated gene array data: qPCR and protein analysis showed significantly elevated Twist1 in sarcoidosis compared to healthy controls. In vitro studies of alveolar macrophages from healthy controls indicated that Twist1 was inducible by classical (M1) macrophage activation stimuli (LPS, TNFα) but not by IL-4, an inducer of alternative (M2) macrophage activation. Findings suggest that Twist1 represents a PPARγ-sensitive alveolar macrophage M1 biomarker which is induced by inflammatory granulomatous disease in the MWCNT model and in human sarcoidosis.

Alveolar macrophages of GM-CSF knockout mice exhibit mixed M1 and M2 phenotypes.

BACKGROUND: Activin A is a pleiotrophic regulatory cytokine, the ablation of which is neonatal lethal. Healthy human alveolar macrophages (AMs) constitutively express activin A, but AMs of patients with pulmonary alveolar proteinosis (PAP) are deficient in activin A. PAP is an autoimmune lung disease characterized by neutralizing autoantibodies to Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF). Activin A can be stimulated, however, by GM-CSF treatment of AMs in vitro. To further explore pulmonary activin A regulation, we examined AMs in bronchoalveolar lavage (BAL) from wild-type C57BL/6 compared to GM-CSF knockout mice which exhibit a PAP-like histopathology. Both human PAP and mouse GM-CSF knockout AMs are deficient in the transcription factor, peroxisome proliferator activated receptor gamma (PPARγ). RESULTS: In sharp contrast to human PAP, activin A mRNA was elevated in mouse GM-CSF knockout AMs, and activin A protein was increased in BAL fluid. Investigation of potential causative factors for activin A upregulation revealed intrinsic overexpression of IFNγ, a potent inducer of the M1 macrophage phenotype, in GM-CSF knockout BAL cells. IFNγ mRNA was not elevated in PAP BAL cells. In vitro studies confirmed that IFNγ stimulated activin A in wild-type AMs while antibody to IFNγ reduced activin A in GM-CSF knockout AMs. Both IFNγ and Activin A were also reduced in GM-CSF knockout mice in vivo after intratracheal instillation of lentivirus-PPARγ compared to control lentivirus vector. Examination of other M1 markers in GM-CSF knockout mice indicated intrinsic elevation of the IFNγ-regulated gene, inducible Nitrogen Oxide Synthetase (iNOS), CCL5, and interleukin (IL)-6 compared to wild-type. The M2 markers, IL-10 and CCL2 were also intrinsically elevated. CONCLUSIONS: Data point to IFNγ as the primary upregulator of activin A in GM-CSF knockout mice which in addition, exhibit a unique mix of M1-M2 macrophage phenotypes.

Extracorporeal membrane oxygenation to support whole-lung lavage in pulmonary alveolar proteinosis: salvage of the drowned lungs.

Pulmonary alveolar proteinosis is a rare lung disease characterized by accumulation of lipoproteinaceous material within the alveoli. Therapeutic whole-lung lavage (WLL) under general anesthesia is the standard treatment in patients with progressive symptomatic disease. Severe hypoxemic respiratory failure is uncommon, yet when present poses a technical challenge to performing WLL without further compromising respiratory status. Rarely, hyperbaric chamber or extracorporeal membrane oxygenation (ECMO) has been utilized to perform WLL to manage severe hypoxemia, with venovenous ECMO being used more often. We present a case of hypoxemic and hypercarbic respiratory failure from pulmonary alveolar proteinosis successfully managed by placing the patient on venoarterial ECMO to facilitate the performance of bilateral WLL.

Alveolar macrophage cathelicidin deficiency in severe sarcoidosis.

BACKGROUND: Dysfunctional immune responses characterize sarcoidosis, but the status of cathelicidin, a potent immunoregulatory and antimicrobial molecule, has not been established in clinical disease activity. METHODS: Alveolar macrophage cathelicidin expression was determined in biopsy-proven sarcoidosis patients classified clinically as 'severe' (requiring systemic treatment) or 'non-severe' (never requiring treatment). Bronchoalveolar lavage (BAL) cells from sarcoidosis patients and healthy controls were analyzed for mRNA expression of cathelicidin, vitamin D receptor (VDR) and the VDR coactivator steroid receptor coactivator-3 (SRC3) by quantitative PCR. Cathelicidin-derived peptide LL-37 was determined by immunocytochemistry. Serum calcidiol (25-hydroxyvitamin D2; vitD2) and calcitriol (1,25-dihydroxyvitamin D3; vitD3) were quantified. RESULTS: The results indicated reduced BAL cell expression of cathelicidin and SRC3 in severe but not non-severe sarcoidosis compared to controls. Serum levels of biologically active vitD3 in both severe and non-severe patients were within the control range even though vitD2 levels in both groups were below the recommended level (30 ng/ml). Sarcoidosis and control alveolar macrophages were studied in vitro to determine cathelicidin responses to vitD3 and tumor necrosis factor-α (TNFα), a vitD3 antagonist elevated in active sarcoidosis. Alveolar macrophage cathelicidin was stimulated by vitD3 but repressed by TNFα, which also repressed SRC3. CONCLUSIONS: These findings suggest that TNFα-mediated repression of SRC3 contributes to alveolar macrophage cathelicidin deficiency in severe sarcoidosis despite healthy vitD3 levels. Deficiency of cathelicidin, a multifunctional regulator of immune cells and proinflammatory cytokines, may impede resolution of inflammation in the lungs of patients with severe sarcoidosis.

Rituximab therapy in pulmonary alveolar proteinosis improves alveolar macrophage lipid homeostasis.

RATIONALE: Pulmonary Alveolar Proteinosis (PAP) patients exhibit an acquired deficiency of biologically active granulocyte-macrophage colony stimulating factor (GM-CSF) attributable to GM-CSF specific autoantibodies. PAP alveolar macrophages are foamy, lipid-filled cells with impaired surfactant clearance and markedly reduced expression of the transcription factor peroxisome proliferator-activated receptor gamma (PPARγ) and the PPARγ-regulated ATP binding cassette (ABC) lipid transporter, ABCG1. An open label proof of concept Phase II clinical trial was conducted in PAP patients using rituximab, a chimeric murine-human monoclonal antibody directed against B lymphocyte specific antigen CD20. Rituximab treatment decreased anti-GM-CSF antibody levels in bronchoalveolar lavage (BAL) fluid, and 7/9 patients completing the trial demonstrated clinical improvement as measured by arterial blood oxygenation. OBJECTIVES: This study sought to determine whether rituximab therapy would restore lipid metabolism in PAP alveolar macrophages. METHODS: BAL samples were collected from patients pre- and 6-months post-rituximab infusion for evaluation of mRNA and lipid changes. RESULTS: Mean PPARγ and ABCG1 mRNA expression increased 2.8 and 5.3-fold respectively (p ≤ 0.05) after treatment. Lysosomal phospholipase A2 (LPLA2) (a key enzyme in surfactant degradation) mRNA expression was severely deficient in PAP patients pre-treatment but increased 2.8-fold post-treatment. In supplemental animal studies, LPLA2 deficiency was verified in GM-CSF KO mice but was not present in macrophage-specific PPARγ KO mice compared to wild-type controls. Oil Red O intensity of PAP alveolar macrophages decreased after treatment, indicating reduced intracellular lipid while extracellular free cholesterol increased in BAL fluid. Furthermore, total protein and Surfactant protein A were significantly decreased in the BAL fluid post therapy. CONCLUSIONS: Reduction in GM-CSF autoantibodies by rituximab therapy improves alveolar macrophage lipid metabolism by increasing lipid transport and surfactant catabolism. Mechanisms may involve GM-CSF stimulation of alveolar macrophage ABCG1 and LPLA2 activities by distinct pathways.

Alveolar macrophage activation in obese patients with obstructive sleep apnea.

BACKGROUND: Classically, activated macrophages in adipose tissue, liver, and muscle have been implicated in many conditions associated with obesity, including insulin resistance and the metabolic syndrome. Despite numerous pulmonary comorbidities and the sentinel role alveolar macrophages play in innate immunity and lung homeostasis, their activation status has not been examined in these patients. Peroxisome proliferator-activated receptor-gamma (PPAR-γ) has been shown to be a negative regulator of inflammation in addition to regulating lipid and glucose metabolism. PPAR-γ is expressed constitutively in healthy alveolar macrophages and decreased on activation. We hypothesized that PPAR-γ would be downregulated in alveolar macrophages from obese patients with obstructive sleep apnea (OSA) in the absence of overt lung disease. METHODS: Alveolar macrophages were obtained by bronchoalveolar lavage from obese individuals with and without OSA and healthy controls. RESULTS: Data indicated that PPAR-γ functional activity was decreased by 48% in obese with OSA and 26% without OSA (P < .05). In obese patients with OSA, PPAR-γ mRNA was decreased 2-fold compared with controls (P < .05), whereas obese patients without OSA, it was not different. Regardless of OSA, alveolar macrophages of obese patients demonstrated increased interleukin-6 mRNA. CONCLUSION: These findings are consistent with the presence of classic macrophage activation and an inflammatory lung environment. Data from this study suggest that alveolar macrophage dysfunction becomes aggravated in OSA and may increase pulmonary disease susceptibility.

Novel murine model of chronic granulomatous lung inflammation elicited by carbon nanotubes.

Lung granulomas are associated with numerous conditions, including inflammatory disorders, exposure to environmental pollutants, and infection. Osteopontin is a chemotactic cytokine produced by macrophages, and is implicated in extracellular matrix remodeling. Furthermore, osteopontin is up-regulated in granulomatous disease, and osteopontin null mice exhibit reduced granuloma formation. Animal models currently used to investigate chronic lung granulomatous inflammation bear a pathological resemblance, but lack the chronic nature of human granulomatous disease. Carbon nanoparticles are generated as byproducts of combustion. Interestingly, experimental exposures to carbon nanoparticles induce pulmonary granuloma-like lesions. However, the recruited cellular populations and extracellular matrix gene expression profiles within these lesions have not been explored. Because of the rapid resolution of granulomas in current animal models, the mechanisms responsible for persistence have been elusive. To overcome the limitations of previous models, we investigated whether a model using multiwall carbon nanoparticles would resemble chronic human lung granulomatous inflammation. We hypothesized that pulmonary exposure to multiwall carbon nanoparticles would induce granulomas, elicit a macrophage and T-cell response, and mimic other granulomatous disorders with an up-regulation of osteopontin. This model demonstrates: (1) granulomatous inflammation, with macrophage and T-cell infiltration; (2) resemblance to the chronicity of human granulomas, with persistence up to 90 days; and (3) a marked elevation of osteopontin, metalloproteinases, and cell adhesion molecules in granulomatous foci isolated by laser-capture microdissection and in alveolar macrophages from bronchoalveolar lavage. The establishment of such a model provides an important platform for mechanistic studies on the persistence of granuloma.

Restoration of PPARγ reverses lipid accumulation in alveolar macrophages of GM-CSF knockout mice.

Pulmonary alveolar proteinosis (PAP) is a lung disease characterized by a deficiency of functional granulocyte macrophage colony-stimulating factor (GM-CSF) resulting in surfactant accumulation and lipid-engorged alveolar macrophages. GM-CSF is a positive regulator of PPARγ that is constitutively expressed in healthy alveolar macrophages. We previously reported decreased PPARγ and ATP-binding cassette transporter G1 (ABCG1) levels in alveolar macrophages from PAP patients and GM-CSF knockout (KO) mice, suggesting PPARγ and ABCG1 involvement in surfactant catabolism. Because ABCG1 represents a PPARγ target, we hypothesized that PPARγ restoration would increase ABCG1 and reduce macrophage lipid accumulation. Upregulation of PPARγ was achieved using a lentivirus expression system in vivo. GM-CSF KO mice received intratracheal instillation of lentivirus (lenti)-PPARγ or control lenti-eGFP. Ten days postinstillation, 79% of harvested alveolar macrophages expressed eGFP, demonstrating transduction. Alveolar macrophages showed increased PPARγ and ABCG1 expression after lenti-PPARγ instillation, whereas PPARγ and ABCG1 levels remained unchanged in lenti-eGFP controls. Alveolar macrophages from lenti-PPARγ-treated mice also exhibited reduced intracellular phospholipids and increased cholesterol efflux to HDL, an ABCG1-mediated pathway. In vivo instillation of lenti-PPARγ results in: 1) upregulating ABCG1 and PPARγ expression of GM-CSF KO alveolar macrophages, 2) reducing intracellular lipid accumulation, and 3) increasing cholesterol efflux activity.

Montelukast added to fluticasone propionate does not alter inflammation or outcomes.

BACKGROUND: Airway inflammation is a key pathological feature of asthma which underlies its clinical presentation. OBJECTIVES: To examine whether adding a leukotriene modifier to an inhaled corticosteroid produces further clinical and/or anti-inflammatory benefits in patients symptomatic on short-acting beta(2)-agonists. METHODS: Patients uncontrolled on short-acting beta(2)-agonists were treated for 12 weeks with either fluticasone propionate (100mcg BD) or fluticasone propionate (100mcg BD) and montelukast (10mg QD) in a randomized, double-blind, parallel group study. Bronchoscopy with endobronchial biopsy and bronchoalveolar lavage (BAL) was performed before and after treatment to compare effects on airway inflammation. RESULTS: Of 103 subjects enrolled, 89 subjects completed treatment and 82 subjects had matched pair biopsy samples. Submucosal eosinophil counts, the primary endpoint, and asthma control improved to similar extents after both treatments (p

PPARgamma regulates the expression of cholesterol metabolism genes in alveolar macrophages.

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear transcription factor involved in lipid metabolism that is constitutively expressed in the alveolar macrophages of healthy individuals. PPARgamma has recently been implicated in the catabolism of surfactant by alveolar macrophages, specifically the cholesterol component of surfactant while the mechanism remains unclear. Studies from other tissue macrophages have shown that PPARgamma regulates cholesterol influx, efflux, and metabolism. PPARgamma promotes cholesterol efflux through the liver X receptor-alpha (LXRalpha) and ATP-binding cassette G1 (ABCG1). We have recently shown that macrophage-specific PPARgamma knockout (PPARgamma KO) mice accumulate cholesterol-laden alveolar macrophages that exhibit decreased expression of LXRalpha and ABCG1 and reduced cholesterol efflux. We hypothesized that in addition to the dysregulation of these cholesterol efflux genes, the expression of genes involved in cholesterol synthesis and influx was also dysregulated and that replacement of PPARgamma would restore regulation of these genes. To investigate this hypothesis, we have utilized a Lentivirus expression system (Lenti-PPARgamma) to restore PPARgamma expression in the alveolar macrophages of PPARgamma KO mice. Our results show that the alveolar macrophages of PPARgamma KO mice have decreased expression of key cholesterol synthesis genes and increased expression of cholesterol receptors CD36 and scavenger receptor A-I (SRA-I). The replacement of PPARgamma (1) induced transcription of LXRalpha and ABCG1; (2) corrected suppressed expression of cholesterol synthesis genes; and (3) enhanced the expression of scavenger receptors CD36. These results suggest that PPARgamma regulates cholesterol metabolism in alveolar macrophages.

Targeted PPAR{gamma} deficiency in alveolar macrophages disrupts surfactant catabolism.

Surfactant accumulates in alveolar macrophages of granulocyte-macrophage colony-stimulating factor (GM-CSF) knockout (KO) mice and pulmonary alveolar proteinosis (PAP) patients with a functional loss of GM-CSF resulting from neutralizing anti-GM-CSF antibody. Alveolar macrophages from PAP patients and GM-CSF KO mice are de-ficient in peroxisome proliferator-activated receptor-gamma (PPARgamma) and ATP-binding cassette (ABC) lipid transporter ABCG1. Previous studies have demonstrated that GM-CSF induces PPARgamma. We therefore hypothesized that PPARgamma promotes surfactant catabolism through regulation of ABCG1. To address this hypothesis, macrophage-specific PPARgamma (MacPPARgamma) knockout mice were utilized. MacPPARgamma KO mice develop foamy, lipid-engorged Oil Red O positive alveolar macrophages. Lipid analyses revealed significant increases in the cholesterol and phospholipid contents of MacPPARgamma KO alveolar macrophages and extracellular bronchoalveolar lavage (BAL)-derived fluids. MacPPARgamma KO alveolar macrophages showed decreased expression of ABCG1 and a deficiency in ABCG1-mediated cholesterol efflux to HDL. Lipid metabolism may also be regulated by liver X receptor (LXR)-ABCA1 pathways. Interestingly, ABCA1 and LXRbeta expression were elevated, indicating that this pathway is not sufficient to prevent surfactant accumulation in alveolar macrophages. These results suggest that PPARgamma mediates a critical role in surfactant homeostasis through the regulation of ABCG1.

Alveolar proteinosis syndrome: pathogenesis, diagnosis, and management.

PURPOSE OF REVIEW: This review discusses the most recent clinical and basic research literature on pulmonary alveolar proteinosis (PAP) as it relates to pathogenesis, diagnosis, and management. RECENT FINDINGS: The discovery of Granulocyte macrophage-colony stimulating factor (GM-CSF) and the alveolar macrophage as critical regulators of surfactant protein and lipid homeostasis has led to significant advances in PAP. Adults affected by PAP have circulating neutralizing anti-GM-CSF antibodies. Reduced localized GM-CSF activity in the lung (from neutralizing anti-GM-CSF antibodies), decreases alveolar macrophage surfactant degradation with surfactant excess and accumulation. Cause, source of antibodies or downstream effects of GM-CSF deficiency is speculative. GM-CSF antibodies above a threshold level have proved to be a useful diagnostic test. Research towards therapy has focused on improving the technique for therapeutic whole lung lavage as well as overcoming effects of neutralizing anti-GM-CSF, which include GM-CSF therapy (systemic and inhaled) and anecdotal reports of anti-B cell therapy. Whereas this approach has been somewhat successful for primary PAP, other causes of PAP (i.e. alveolar macrophage dysfunction, surfactant protein alterations) are still without therapy. SUMMARY: Understanding of the pathogenesis of PAP has greatly increased in the last decade; study has brought better comprehension of lung biology and recognition of the critical role for GM-CSF and alveolar macrophage in surfactant clearance. Balance between resident immune cell population and normal lung function still needs further study. Resident alveolar macrophages have an essential role in surfactant homeostasis. With this knowledge more effective diagnostic tests (e.g. anti-GM-CSF antibody) and therapies for PAP are under investigation.

Deletion of PPAR gamma in alveolar macrophages is associated with a Th-1 pulmonary inflammatory response.

Peroxisome proliferator-activated receptor gamma (PPARgamma) is constitutively expressed at high levels in healthy alveolar macrophages, in contrast to other tissue macrophages and blood monocytes. PPARgamma ligands have been shown to down-regulate IFN-gamma-stimulated inducible NO synthase (iNOS) in macrophages. Because NO is an important inflammatory mediator in the lung, we hypothesized that deletion of alveolar macrophage PPARgamma in vivo would result in up-regulation of iNOS and other inflammatory mediators. The loss of PPARgamma in macrophages was achieved by crossing floxed (+/+) PPARgamma mice and a transgenic mouse containing the CRE recombinase gene under the control of the murine M lysozyme promoter (PPARgammaKO). Alveolar macrophages were harvested by bronchoalveolar lavage (BAL). Lymphocytes (CD8:CD4 ratio = 2.8) were increased in BAL of PPARgammaKO vs wild-type C57BL6; p < or = 0.0001. Both iNOS and IFN-gamma expression were significantly elevated (p < or = 0.05) in BAL cells. Th-1 associated cytokines including IL-12 (p40), MIP-1alpha (CCL3), and IFN inducible protein-10 (IP-10, CXCL10) were also elevated. IL-4 and IL-17A were not detected. To test whether these alterations were due to the lack of PPARgamma, PPARgamma KO mice were intratracheally inoculated with a PPARgamma lentivirus construct. PPARgamma transduction resulted in significantly decreased iNOS and IFN-gamma mRNA expression, as well as reduced BAL lymphocytes. These results suggest that lack of PPARgamma in alveolar macrophages disrupts lung homeostasis and results in a Th1-like inflammatory response.

A novel 1,25-dihydroxyvitamin D-activin A pathway in human alveolar macrophages is dysfunctional in patients with pulmonary alveolar proteinosis (PAP).

We have shown that activin A, a cytokine implicated in regulating B-cell proliferation, is severely deficient in alveolar macrophages from patients with pulmonary alveolar proteinosis (PAP), an autoimmune disorder characterized by surfactant accumulation and neutralizing autoantibodies to granulocyte-macrophage colony stimulating factor. Mechanisms of activin regulation in alveolar macrophages are not well understood. Based on previous gene array results from PAP bronchoalveolar lavage cells suggesting deficiencies in vitamin D target genes, and on recent evidence of vitamin D receptor elements (VDREs) in the human activin A gene promoter, we investigated the effects of 1,25-dihydroxyvitamin D (vitamin D(3)) on activin A expression in alveolar macrophages from healthy individuals and PAP patients. Activin A expression was stimulated by LPS in cultures of either healthy control or PAP alveolar macrophages; in contrast, vitamin D(3) increased activin A only in healthy controls but not in PAP. Compared to healthy controls, freshly obtained (uncultured) PAP alveolar macrophages displayed healthy intrinsic vitamin D receptor expression but deficient expression of vitamin D target genes, cathelicidin and thioredoxin interacting protein. PAP patients also demonstrated a relative insufficiency of circulating vitamin D. Investigation of activin A in murine alveolar macrophages confirmed a lack of functional response to vitamin D as anticipated since murine activin A does not contain VDREs. Results suggest that mechanisms of activin A deficiency in PAP alveolar macrophages may involve dysregulation of a novel species-specific vitamin D-activin A pathway.

ABCG1 is deficient in alveolar macrophages of GM-CSF knockout mice and patients with pulmonary alveolar proteinosis.

Patients with pulmonary alveolar proteinosis (PAP) display impaired surfactant clearance, foamy, lipid-filled alveolar macrophages, and increased cholesterol metabolites within the lung. Neutralizing autoantibodies to granulocyte-macrophage colony-stimulating factor (GM-CSF) are also present, resulting in virtual GM-CSF deficiency. We investigated ABCG1 and ABCA1 expression in alveolar macrophages of PAP patients and GM-CSF knockout (KO) mice, which exhibit PAP-like pulmonary pathology and increased pulmonary cholesterol. Alveolar macrophages from both sources displayed a striking similarity in transporter gene dysregulation, consisting of deficient ABCG1 accompanied by highly increased ABCA1. Peroxisome proliferator-activated receptor gamma (PPARgamma), a known regulator of both transporters, was deficient, as reported previously. In contrast, the liver X receptor alpha, which also upregulates both transporters, was highly increased. GM-CSF treatment increased ABCG1 expression in macrophages in vitro and in PAP patients in vivo. Overexpression of PPARgamma by lentivirus-PPARgamma transduction of primary alveolar macrophages, or activation by rosiglitazone, also increased ABCG1 expression. These results suggest that ABCG1 deficiency in PAP and GM-CSF KO alveolar macrophages is attributable to the absence of a GM-CSF-mediated PPARgamma pathway. These findings document the existence of ABCG1 deficiency in human lung disease and highlight a critical role for ABCG1 in surfactant homeostasis.